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iOS 9, thoroughly reviewed

Apple gives the iPad a lot of love as iOS goes back into spit-and-polish mode.

Device compatibility

iOS 9 runs on all the same hardware that ran iOS 8 as well as a few of the things introduced at Apple's September event. Generally speaking, that's great. The iPhone 4S and iPad 2 both showed up in 2011, though both were sold up until last year—most other mobile devices that came out that long ago have long since stopped receiving software updates. The complete list:

The iPhone 4S, 5, 5C, 5S, 6, 6 Plus, 6S, and 6S Plus.

The iPad 2, third- and fourth-generation Retina iPads, both iPad Airs, and all three iPad Minis.

The fifth- and sixth-generation iPods Touch.

Absent from that list is the third-generation Apple TV, which up until now has received updates more or less in lockstep with the rest of the family. The new Apple TV's tvOS is still iOS-based and likely uses iOS 9 as its base, but as of this writing it doesn't look like that courtesy is being extended to the old Apple TV.

Installation and free space

iOS 9 is available as an OTA update or through iTunes for anything that can run iOS 8. The size of the OTA will vary from device to device, but in any case Apple estimates that you'll only need 1.3GB of free space available to install it (this is down from roughly 4.6GB for the iOS 8 OTA). If you can't free up that much space, you'll still be able to install via iTunes.

Both iOS 7 and iOS 8 left iDevices with less usable free space than they had before the update, an understandable but unfortunate side effect of the new features. To calculate the amount of free space iOS 9 takes up, we reset each of the following devices, went through first-time setup without configuring any iCloud or App Store accounts, and then gave the devices a few minutes to "settle." The amount of free space decreases by a few hundred MB even if you don't really do anything, presumably because of Spotlight indexing and other first-time setup activities. The free space readings come from the About page of the Settings app.

Device

Space available (iOS 8.4.1)

Space available (iOS 9.0 GM)

Difference

16GB iPhone 4S (VZW)

11.6GB

11.6GB

None

32GB iPhone 5 (VZW)

26.1GB

26.1GB

None

16GB iPhone 5S (Unlocked)

11.0GB

10.8GB

-0.2GB

64GB iPhone 6 (AT&T)

54.5GB

54.4GB

-0.1GB

16GB iPhone 6 Plus (Unlocked)

10.2GB

10.4GB

+0.2GB

32GB iPod Touch 5

26.5GB

26.3GB

-0.2GB

32GB iPod Touch 6

25.9GB

25.5GB

-0.4GB

16GB iPad 2 (Wi-Fi)

12.4GB

12.3GB

-0.1GB

32GB iPad 4 (Wi-Fi)

25.9GB

26.0GB

+0.1GB

64GB iPad Air 2 (Wi-Fi)

54.7GB

54.6GB

+0.1GB

16GB iPad Mini

12.0GB

11.8GB

-0.2GB

16GB iPad Mini 2

10.7GB

11.1GB

+0.4GB

With just a handful of exceptions, iOS 9 isn't going to give you space back, but, even when it does consume more space than iOS 8.4, its impact is negligible. You rarely lose more than 100 or 200MB. iOS 8 made much larger, far-reaching changes to the platform, but in exchange it routinely gobbled up between 750MB and 1GB of extra space compared to iOS 7.1. This is an improvement.

Out of the box

The first-time setup process for iOS 9 is mostly familiar, though there have been some functional and aesthetic tweaks. On newer devices, there's an option to transfer your data from an Android phone or tablet using Apple's transfer app in Google Play—we'll detail the transfer process in a separate article. TouchID devices need to set a six-digit numerical passcode at a minimum, even if you elect not to use TouchID, a nudge to encourage those users to use TouchID to unlock their phones most of the time. You should only actually need that passcode if you reboot your device or install an update. And while you can still set your iDevices up without an Apple ID and iCloud, the language has been tweaked to push you in that direction, and you need to tap three times instead of two to skip it when you're setting up a new device.

Microsoft changed Windows 10's setup wizard in a similar way—it's possible to use the OS without a Microsoft account, but the setting is buried a bit. That's just the way all of this software is moving: More connected, not less.

Andrew Cunningham

Andrew Cunningham

Andrew Cunningham

Andrew Cunningham

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Andrew Cunningham

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Feature fragmentation

While the older devices on that list still get the same security fixes, design changes, and most of the same APIs as brand-new ones, there are some features that aren't available on older iThings. This is usually either because the hardware is too slow (hello Apple A5) or because some necessary hardware component is missing (no 5GHz Wi-Fi or Bluetooth 4.0 in some devices, no TouchID in others, and so on).

This is an attempt at a comprehensive list, and it includes features that were introduced in earlier versions of iOS as well as hardware-enabled features like Apple Pay and 3D Touch.

Missing iPad features

Siri doesn't work on the iPad 2. Transparency/translucency effects aren't supported on the iPad 2 or third-generation iPad.

Missing iPhone and iPod features

Step-tracking and tracking walking and running distance without external hardware requires an iPhone 5S or newer or a sixth-generation iPod Touch; tracking and elevation without external hardware requires an iPhone 6 or newer or a sixth-generation iPod Touch.

Burst photos, slow-mo video, and related features require an iPhone 5S or newer or a sixth-generation iPod Touch.

App Handoff and Suggested Apps require an iPhone 5 or newer, fourth-generation iPad or newer, any iPad Mini, or either iPod Touch. Handoff for phone calls and SMS messages will work on the iPhone 4S as well.

AirDrop requires an iPhone 5 or newer, fourth-generation iPad or newer, any iPad Mini, or either iPod Touch.

Support for Apple Pay mobile and in-app payments requires an iPhone 6 or newer. The iPad Air 2 and iPad Mini 3 support in-app payments only. The iPhone 5, 5C, and 5S can support it in a roundabout way via the Apple Watch.

"Intelligence" features and Siri suggestions require an iPhone 5 or newer, a fourth-generation iPad or newer, the iPad Mini 2, 3, or 4, or the sixth-generation iPod Touch (Apple A5 devices aren't supported).

Safari Content Blockers require 64-bit hardware. This includes the iPhone 5S or newer, the iPad Air or Air 2, the iPad Mini 2, 3, or 4, or the sixth-generation iPod Touch.

TouchID-related features require an iPhone 5S or newer, an iPad Air 2, or an iPad Mini 3.

OpenGL ES 3.0, the Metal graphics API, and 64-bit ARMv8 apps require an iPhone 5S or later, the iPad Air or Air 2, the iPad Mini 2, 3 or 4, or the sixth-generation iPod Touch.

If you've got hardware from 2013 or 2014, your device is going to support just about everything that iOS 9 offers. Even the iPhone 5, released in 2012, gets most of the important stuff (as does the 5c by extension). Predictably, the iPhone 4S and iPad 2 are left out in the cold the most often.

Further Reading

It's important to note that while we used the often-loaded word "fragmentation" at the beginning of this section, iOS feature fragmentation and the kind of fragmentation you see in the Android ecosystem are completely different. Attempts to compare Android and iOS in this regard are misinformed at best, facetious trolling at worst.

Android is increasingly fragmented not just by major versions, but by Google-approved implementations and the AOSP-based forks of the OS you see on many Chinese devices and on Amazon's Fire hardware. Google has taken major steps forward in recent years (at least for Google-sanctioned Android) by breaking almost all of its Android apps and a few system components out into the Google Play store where they can be updated at will, but improvements and security fixes baked into the OS are still subject to the same carrier- and OEM-introduced delays that have always held them up.

Windows Phone exists somewhere in between. Carrier and OEM approval processes still hold up "final" updates, but Microsoft's preview programs at least offer an officially sanctioned workaround to users who care the most about updates.

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Andrew Cunningham
Andrew wrote and edited tech news and reviews at Ars Technica from 2012 to 2017, where he still occasionally freelances; he is currently a lead editor at Wirecutter. He also records a weekly book podcast called Overdue. Twitter@AndrewWrites